Thermostat



Sept. 15, 1942. s n' 2,296,067

THERMOSTAT Filed March 20, 1939 Jhhhhh Q7 INVENTOR:

'. 29 a wma. h m/z ATTORNEYS Patented Sept. 15,1942 I UNITED STATES PATENT OFFICE ncimaasmita, stlronhllo amlg'norto Knapp-Monarch Company, St. Denis, 110., a corporation of Mimonri Application March so, me, serial No. seam a cums 01 200-138) An object of my present invention is to pro- Figure 5 is a sectional view on the line H oi vide a thermostat of simple and inexpensive con- Figure 4. struction particularly adapted for mounting on Figure 6 is a bottom plan view of a modified waflie iron grids and the like so that it is responform oi structure: and sive to the heat thereof. t 5 Figure 7 is an enlarged sectional view thereof A further object is to provide a thermostat onthelinel-l of Figure 6. which includes a bi-metal element loosely My thermostat can be applied to diilerent elecmounted in a pocket of the thermostat without trical appliances and by way of example Lhave means of rigid connection for the bi-metal ele-- shown a waille iron comprising a base ll having merit, the usual anchorage by means of screws 10 handles it and lower and upper casings I4 and or the like being eliminated from my construcii. The casing M is hinged to the casing II at tion whereby strains and permanent set resulting II in the usual manner and is provided with from such type of anchorage and the attendant handles for opening the waile iron. The lower variations in setting of the thermostat after it casing ll includes a grid ll retained in position has operated for some time are entirely elimi- 1 asbyscrews ll. hated. My thermostat assembly shown in Figure 3 con-,

' 7 Another object is to provide a thermostat assists of a stamping 8 having a bottom plate 2| sembly consisting of a stamping which may be provided with an opening II to receive the screw secured to. a waflie iron grid or the like and which I. A nut 22 serves to retain the stamping B in includes flanges bent away from the frame thereposition against the grid ll.

of to provide a pocket to loosely receive a bi- The bottom plate 20 has a pair of opposed upmetal bar, an adjusting screw and a circuit. turned flanges 23 and another pair of upturned breaker being arranged to engage opposite ends flangea 24 opposed by an upturned flange 2|. of the bar whereby W rpi 0f t e be! to 8 8 The flanges 23, 24 and II constitute a pocket the adjusting screw and the circuit breaker will 25 gorabbmem element 3;

eilect operation of the circuit breaker upon iur- The i em a is a strip or bar or bi-metal of ther warpage oi the bi-metai bar due to a fur-- slightly 1 th t th i tan b tw e th ther increase in temperature flanges 23 and slightly less width than the flanges Still another object is to provide a modified u and 2' so that it is loosely mounted in the form of my construction in which the pocket may pocket and is therefore no to mm m response be cast on the grid and the adjusting screw and to tempemm chm meeting it without my the circuit breaker mounted on bosses projecting possibility of binding within the pocket m is from the grid, whereby the adjusting screw and a very important feature of my mm the circuit breaker may properly overhang the; The ttb plate 2. is provided with upstruck loosely mounted bi-metal bar in the pocket to brackets 21 and adapted to support a 01mm efiect operation of the circuit breaker therefrom. breaker c and an a d1 g screw support a other fi g z fi' fi i' p lvely. The circuit breaker 0 comprises a mes t e pres P block of insulation :0 having contact blades 1| obvious from the accompanying drawings and and a mounted thereon and the circuit b r will be better pointed out as the description r 40 is then mounted b a bolt o the the invention progresses. In describing the in-, on" Th cgcult break 1 d it; vention in detail, reference will be made to the g and b the g acccnmanyingd drawiitieg wherein like reference the Tltbhde I8 r at h 222w ma co a r $332K; 55,53 and W as flexible while the blade :2 is a iecr spring. blade Figurelisaplanviewofawaiheironwithmy' v s m e h contact thermostat mounted in the M thereof and II from the contact 34. Terminals II and 81 are shown in dotted lines m this mm. provided for the blades ti and 31 respectively.-

Flgure 3 is an enlarged sectional View on a The circuit breaker C is arranged to have the line m leaf spring 32 overhang one end of the pocket Figure 3 is a perspective view of my the t t for the bl-metal element 20 and is provided with assembly looking at it from the underneath sur-, a prciecflon ll erminating in an insulatin butiace thereof. ton P 9 e n aged at times by the bi- Figure 4 is a vertical sectional view on the line metal 1,81 The fi Screw s pport ll 4-4 of Figure 2. II overhangs the other end of the pocket for the bimanner.

metal element St and an adjusting screw 40 is threaded therein.

The adjusting screw 40 may be provided with any convenient means to rotate it to secure different degrees of adjustment for the thermostat. By way of illustration, I show an arm 4| extending from the adjusting screw and connected by a link 42 to an arm 43. The arm 43 is mounted on a shaft 44 journaled in the base II and provided with an adjusting knob 45 on top of the base.

In Figures 6 and 7 I show a modified construction in which a grid Ila has walls or flanges Ila, 24a and 25a cast thereon. These walls form a pocket for the bi-metal element 46, while the circuitbreaker C and the adjusting screw support 29 are mounted on bosses 21a and 28a formed on the grid.

In Figure 6 I have shown the circuit connections to a heating element H which includes the usual resistance wire 41. The terminals of the resistance wire are indicated at 48 and 49. Current supply wires L and L supply current to the terminals 48 and to the terminal 36 of the circuit breaker. The other terminal 31 of the circuit breaker is connected by a wire a to the terminal 48. Thus the circuit breaker is connected in series with the heating element H in the usual Practical operation Referring to Figure 54c will be noted that the bi-metal bar 25 is resting on the adjusting screw 40 and the insulating button 39 of the circuit breaker C. Since the bi-metal element is loose in its pocket and the pocket is inverted, this is the position it will normally asume. Upon an increase in temperature the center of the bar will warp upwardly and finally strike the bottom plate 20 of the bi-metal element pocket. Thereafter further warping will result in the button 39 being depressed and the circuit breaker thereby operated to open the circuit to the heating element H. Obviously with the adjusting screw 40 at different elevations, the circuit breaker C will be operated at different temperatures.

The stamping S provides a convenient arrangement for pre-fabrication of the thermostat assembly, which can then be tested and adjusted before being mounted on the waffle iron. The nut 22 serves as a convenient means for mounting the stamping'S against the grid la in such manner that the heat of the grid is effectively transmitted by the stamping to the bimetal bar within the pocket thereof. For this purpose the stamping may be made of brass, aluminum or the like so as to facilitate conduction of the heat.

The form of invention shown in Figure 6 operates in a similar manner but does not lend itself to pre-fabrication of the thermostat.

My type of thermostat in which the bi-metal element is floatingly mounted eliminates the strain of an anchorage as usually provided for bimetal elements. When one end of the element is anchored, the strains set up in the metal sometime result in a permanent set to the element which causes inaccurate operation of the thermostat thereafter. All possibility of such undesirable operation is eliminated with my construction in which the bi-metal element is free to operate without restriction from an anchorage or other means rigidly connected with the bimetal element.-

In accordance with the provisions of the patpocket upon be ent statutes I have described my invention and also the principle of operation thereof. On my drawing I have illustrated what I consider to represent the best embodiments thereof but desire to have it understood that the structure disclosed is illustrative only and that the invention may be carried out by other means within the scope of the appended claims.

I claim:

1. In a thermostat for a grid or the like heated by an electric heating element, a pocket on said grid, an adjusting screw projecting into said pocket, a loose bi-metal element located therein and of smaller size thansaid pocket to permit free movement of the bi-metal element in the in; warped by response to increased temperature, said bi-metal element being unconnected with said pocket and a circuit breaker for controlling the circuit of the heating element, said circuit breaker being operated to open circuit position by said bi-metal element only after a predetermined degree of warping thereof in said pocket sufllcient to cause simultaneous engagement of three spaced points of said bimetal element with one point of said pocket, with said adjusting screw, and with said circuit breaker respectively.

2. In a thermostat, a grid or the like, a pocket on said grid, a free bi-metal element loosely mounted therein, a circuit breaker engaged by one portion of said bi-metal element uponwarpage thereof to a predetermined position of said portion under the influence of an increase in temperature of said grid and an adjusting element engageable with another portion of said himetal element and movable to various distances from the bottom of said pocket to vary said predetermined position at which said bi-metal element operates said circuit breaker, the portion of said bi-metal element intermediate said two first mentioned portions thereof engaging said bottom of said pocket to effect operation of said circuit breaker upon warpage to said predetermined position.

3. In a thermostat for a grid or the like, a pocket member, a free bi-metal element loosely mounted therein, a circuit breaker engaged by one portion of said bi-metal element upon warpage thereof to a predetermined position of said portion under the influence of an increase in temperature of the grid and a pair of abutments for two other portions of said bi-metal element to engage upon such warpage, one of said pair of abutments constituting a range adjusting device for said thermostat.

4. In a thermostat, an element to be heated, a pocket thereon, a loose bi-metal element mounted in said pocket for free movement therein, a circuit. breaker engaged by said bi-metal element upon warpage thereof to a predetermined position under the influence of an increase in temperature" of said grid, and an adjusting element directly engageable with another portion of said bi-metal element and movable to various positions to vary the point at which the adjusting element is engaged by said bi-metal element and thereby varying said predetermined position at which said bi-metal element operates said circuit breaker, said bimetal element being engaged with a wall of said pocket upon such warpage to said predetermined position.

5. A thermostat comprising a stamping for mounting on a device tobe heated, said stamping being formed with a pocket, a loose bi-metal element received in said pocket, said element being oi less diameter than said pocket, a circuit breaker supported by said stamping and adapted to be engaged by one point on said bimetal element and thereby operated by said bi-metal element as the element warps in said pocket to a predetermined position under the influence oi heat conducted to the pocket by said stamping and an adjusting member supported by said stamping and variable relative thereto, said member being arranged to form an abutment i'or another point of said bi-metal element to engage and thus predetermine the position with relation to the-heat r aifectingsaid pocket at which said bi-metal element engage the pocket at a third point and said circuit breaker is engaged and operated by the bi-metal element.

'6 A thermostat comprising a stamping for mounting on a grid or the like, said stamping having a pocket formed therein, a free bi-metal element loosely received in and unconnected with said pocket, a circuit breaker supported by said stamping and adapted to be engaged and operated by said bi-metal element as it warps in said pocket to a predetermined position under the influence of heat from the grid being conducted to the pocket by said stamping, said bimetal element thereupon engaging, at two spaced points thereon, with a point of said pocket and with said circuit breaker and an adjusting screw supported by said stamping and variable relative thereto, said screw being arranged to form an abutment for a third point of said bi-metal element to engage simultaneously with the engagement of said two points and thus predetermine the position at which said circuit breaker is operated.

'l. A thermostat comprising a stamping having flanges bent away from the plane thereof to form an elongated pocket, a loose -bi-metal bar mounted in said pocket and ofslightly smaller size than the distance between said flanges whereby to permit free movement of the bi-metal element in the pocket due to warpage thereof screw and with said circuit breaker whereby simultaneous engagement of the bi-metal element with the pocket, the screw and the circuit breaker, and thereafter further warping of the bi metal element in response to a further increase in heat, will operate said circuit breaker.

8. A thermostat comprising a stamping having flanges bent away from the plane thereof to form an elongated pocket, a free bi-metal bar loosely mounted in said pocket to permit freewarpage of the bi-metal element therein, a circuit breaker supported by said stamping and over-hanging said pocket, an adjusting element supported by said stamping and also overhanging said pocket, the ends of said bi-metal element being engageable with said adjusting element and said circuit breaker whereby simultaneous engagement with the two and with said pocket intermediate the ends of the bi-metal element, and thereafter further warping of the bi-metal element will operatesaid circuit breaker.

HOWARD A. SMITH. 

